KIKIMR-25621: Introduce multi-column statistics

#### Introduce multi-column statistics support ✎

- Adds support for defining multi-column statistics in table schemas, allowing users to specify statistics for combinations of columns rather than individual columns
- Introduces new SQL syntax for CREATE TABLE and ALTER TABLE statements to declare statistics with optional type specifications
- Implements validation for statistics definitions, ensuring column references are valid and names are unique
- Extends the query processing pipeline to handle statistics declarations during table creation and modification operations
- Updates syntax highlighting and parsing rules to recognize the new statistics keyword and related constructs
- Adds comprehensive unit tests covering various statistics scenarios including multi-column definitions, type specifications, and validation rules

<a href="https://nda.ya.ru/t/qa0kX64r7DqvtN"><font size="2">Autodescription by Yandex Code Assistant</font></a>
commit_hash:5ca3f8721d3e3660f2bb890c1408e420cf7c3e81

1 files changed, 30 insertions, 2 deletions

diff --git a/yql/essentials/sql/v1/sql_query.cpp b/yql/essentials/sql/v1/sql_query.cpp
index 4983e961f60..45d2b5b79c2 100644
--- a/yql/essentials/sql/v1/sql_query.cpp
+++ b/yql/essentials/sql/v1/sql_query.cpp
@@ -2565,7 +2565,9 @@ bool TSqlQuery::AlterTableAction(const TRule_alter_table_action& node, TAlterTab
         case TRule_alter_table_action::kAltAlterTableAction10: {
             // DROP INDEX
             const auto& dropIndex = node.GetAlt_alter_table_action10().GetRule_alter_table_drop_index1();
-            AlterTableDropIndex(dropIndex, params);
+            if (!AlterTableDropIndex(dropIndex, params)) {
+                return false;
+            }
             break;
         }
         case TRule_alter_table_action::kAltAlterTableAction11: {
@@ -2692,6 +2694,22 @@ bool TSqlQuery::AlterTableAction(const TRule_alter_table_action& node, TAlterTab
 
             break;
         }
+        case TRule_alter_table_action::kAltAlterTableAction24: {
+            // ADD STATISTICS
+            const auto& addStatistics = node.GetAlt_alter_table_action24().GetRule_alter_table_add_statistics1();
+            if (!AlterTableAddStatistics(addStatistics, params)) {
+                return false;
+            }
+            break;
+        }
+        case TRule_alter_table_action::kAltAlterTableAction25: {
+            // DROP STATISTICS
+            const auto& dropStatistics = node.GetAlt_alter_table_action25().GetRule_alter_table_drop_statistics1();
+            if (!AlterTableDropStatistics(dropStatistics, params)) {
+                return false;
+            }
+            break;
+        }
         case TRule_alter_table_action::ALT_NOT_SET:
             YQL_ENSURE(false, "Unreachable");
     }
@@ -3025,8 +3043,18 @@ bool TSqlQuery::AlterTableAddIndex(const TRule_alter_table_add_index& node, TAlt
     return CreateTableIndex(node.GetRule_table_index2(), params.AddIndexes);
 }
 
-void TSqlQuery::AlterTableDropIndex(const TRule_alter_table_drop_index& node, TAlterTableParameters& params) {
+bool TSqlQuery::AlterTableDropIndex(const TRule_alter_table_drop_index& node, TAlterTableParameters& params) {
     params.DropIndexes.emplace_back(IdEx(node.GetRule_an_id3(), *this));
+    return !Ctx_.HasPendingErrors;
+}
+
+bool TSqlQuery::AlterTableAddStatistics(const TRule_alter_table_add_statistics& node, TAlterTableParameters& params) {
+    return CreateTableStatistics(node.GetRule_table_statistics2(), params.AddStatistics);
+}
+
+bool TSqlQuery::AlterTableDropStatistics(const TRule_alter_table_drop_statistics& node, TAlterTableParameters& params) {
+    params.DropStatistics.emplace_back(IdEx(node.GetRule_an_id3(), *this));
+    return !Ctx_.HasPendingErrors;
 }
 
 void TSqlQuery::AlterTableRenameTo(const TRule_alter_table_rename_to& node, TAlterTableParameters& params) {